Experimental Development and Calibration of (U-Th)/He Thermochronology

REINERS EAR-0073576最近人们对(U-Th)/He测年的兴趣重新抬头，这是由于解释方面的进展与仔细的扩散研究相结合，以及明显成功的构造应用和与其他温度计时器的校准。然而，他约会的许多令人兴奋的方面仍然没有被探索。这项工作包括一系列实验研究，以开发、推广和校准新的(U-Th)/He热年代学方法。一个目标是将他的测年延长到新的相，包括锆石、萤石和石榴石。这是因为在缺乏这些相的岩石(如许多沉积和热液矿化的岩石)中存在低T热约束的潜在好处，以及其他相独特的扩散特性和闭合温度(TC)。第二个目标是利用He的扩散域等同于晶体或颗粒本身的特性。我们将试图利用这一点不仅限制冷却年龄，而且限制晶体的热历史，通过检查1)使用磨损技术在单个晶体内的核心到边缘He浓度和年龄分区的潜在用途，以及2)反映部分重置晶体的特定热历史的年龄-颗粒尺寸关联。最后一个目标是将(U-Th)/He热计时方法与其他方法进行严格的比较，主要是多域钾长石40Ar/39Ar测年，以提供方法间校准和前所未有的密集时间-温度采样和热约束。南加州大学的(U-Th)/He实验室将于2000年5月开始测量年龄和进行扩散实验，这笔资金将为致力于这些方法的实验开发的研究生提供支持，合作伙伴包括区域裂变径迹和40Ar/39Ar热年代学实验室、南加州大学和附近的伊利诺伊大学的经济地质学项目。

ReinersEAR-0073576Recent resurgence of interest in (U-Th)/He dating has been made possible by interpretational advances combined with careful diffusion studies and apparently successful tectonic applications and calibrations against other thermochronometers. Nevertheless, many exciting aspects of He dating remain unexplored. This work comprises a series of experimental studies to develop, extend, and calibrate new (U-Th)/He thermochronologic methods. One objective is to extend He dating to new phases, including zircon, fluorite, and garnet. This is motivated by the potential benefits of low-T thermal constraints in rocks that lack these phases in abundance such as many sedimentary and hydrothermally mineralized rocks, as well as the unique diffusion properties and closure temperatures (Tc) of other phases. A second objective is to exploit the property that the diffusion domain for He is equivalent to the crystal or grain itself. We will attempt to use this to constrain not only cooling ages, but thermal histories of crystals, by examining the potential uses of 1) core-to-rim He concentration and age zonation within individual crystals using abrasion techniques, and 2) age-grain size correlations that reflect specific thermal histories of partially reset crystals. A final objective is to rigorously compare (U-Th)/He thermochronometry with other methods, primarily multi-domain K-feldspar 40Ar/39Ar dating to provide intermethodcalibrations and unprecedentedly dense time-temperature sampling and thermal constraints. The (U-Th)/He lab at W.S.U. is set to begin measuring ages and performing diffusion experiments in May of 2000, and this funding will provide support for graduate students working on experimental development of these methods, in collaboration with with regional fission-track and 40Ar/39Ar thermochronologic labs, the economic geology programs at W.S.U. and the nearby U.I.